LCD Glossary

The area of the display or touch panel that is useful for touch or viewing.

Active Matrix = AMLCD (See also TFT)

Active matrix liquid crystal display (LCD). A Liquid crystal based display technology that uses a switch at each pixel to create high resolution and fast response times. One type of LCD is known as thin film transistor (TFT) LCD, in which the switch used is a thin film transistor. Displays based on this technology range from as small as 1" diagonal up to 100" diagonal.

Active Plate

Another term for the glass substrate that contains the array or thin film transistors (TFTs) in an active matrix liquid crystal display (LCD). This is also known as an array or backplane.

Amorphous silicon (a-Si)

A semiconductor film used as the active layer in most active matrix liquid crystal displays (LCDs). It is based upon the electronic properties of a glass alloy of silicon and hydrogen.

Analog to Digital Controller:

A controller which converts an analog signal to a digital signal thus providing the input to the display in a digital format.

Analog Resistive Touch Panel:

This touch panel is comprised of two transparent resistive layers, separated by small spacers. Touching the screen causes the two layers to come in contact and form a switch closure. By measuring the voltage gradient in the horizontal and vertical axis, position can be determined.

Analog RGB:

Separate Red, green, and blue video signals used in conjunction with composite sync or separate horizontal and vertical sync.

Analog Signal:

A signal that travels continuously. An analog signal may be either direct or alternating current.

Array

Rows and columns of thin-film-transistors (TFTs) made on a glass substrate to form the pixel-addressing component of an active matrix liquid crystal display (LCD). The TFTs are made by depositing a series of films via chemical vapor deposition and patterning these films by photolithography. This process is very similar to the manufacturing process for silicon-based microelectronics. This is also known as a backplane.

The light source for an active matrix liquid crystal display (LCD), located behind the panel. It is usually made up of several fluorescent lamps, a light guide, reflectors, and brightness enhancing films.

Backplane

Another name for thin film transistor (TFT) array (see Array). TFT backplanes can be used to make active matrix liquid crystal displays (LCDs) or organic light emitting diode (OLED) displays.

Bezel:

Secures the LCD to the printed circuit board. Can be plastic or metal.

Bias Voltage:

A voltage applied to a circuit or device to establish a reference level or operating point of the device during testing.

Black Matrix

A light-shielding film that separates the pixels of the color filter.

Borosilicate

A family of glass compositions in which boron trioxide and silicon dioxide are major components.

Brightness

This is the measure of the luminosity in a display, expressed in nits or candelas/meter2.

Burn-in

A tendency for an image that is shown on a display over a long period of time to become permanently fixed on the display. This is most often seen in emissive displays such as CRT (cathode ray tube) and plasma, because chemical changes can occur in the phosphors when exposed repeatedly to the same electrical signals. This is most noticeable in electronic signage such as in airport information displays, or displays that are used with video games, and is less noticeable in consumer televisions.

A display that is used to display letters, numbers, and symbols only. Typically described as Number of lines by number of characters.

COB:

Chip on Board. The LCD driver is epoxied onto the PCB and wire bonds are installed for connections to the IC. The chip plus bonding wires are covered with black epoxy as a seal.

COG

Chip-on-glass, a method of bonding driver integrated circuits (ICs) directly to the edges of active matrix liquid crystal displays (LCDs) for smaller packages, higher quality, and improved ruggedness. The driver IC is mounted upside down (flip chip) eliminating bond wires and interconnects. Reliability is improved due to reduction in interconnects.

COF:

Chip on Flex. The LCD driver is incorporated into a flex connector, which is attached by a heat seal method to the contact edge of the LCD glass.

Color Filter

A component of the active matrix liquid crystal display (LCD) panel. The color filter contains primary colors - red, green and blue - that enable the LCD to produce more than 16 million colors.

Colors:

· 3-Bit = 512 colors

· 4-Bit = 4096 colors

· 6-Bit = 262K colors

· 8-Bit = 16M colors

Contrast Ratio:

The ratio of the luminance in the light state to that of the dark side.

Controller:

An IC, usually mounted in the graphics board, which takes the microprocessor output and tells the display which pixels to light up to produce the image requested.

CRT

Cathode ray tube (CRT), a technology used in many traditional television sets and desktop computers. A CRT uses a vacuum tube that produces images when an electron beam strikes a phosphorescent surface. CRT devices are bulkier and require more space than active matrix liquid crystal display (LCD) devices.

CSTN

Color Super Twisted Nematic. A passive matrix display technology used to produce low cost color displays without resorting to TFT manufacturing technology. Color STN Technology is actually STN technology that uses a white backlight and color filters to produce the hues required for a color display. Each visual pixel of a CSTN display is actually 3 separate pixels using a colored filter of Red. Green, and Blue. Each of those colors is controlled individually by the graphic controller chip. So actually a 320 by 240 pixel CSTN display contains 960 by 240 individually colored pixels.

CTE

Coefficient of thermal expansion (CTE). The slope of the expansion versus temperature curve. For glasses, it is typically expressed as a value multiplied by 10-7/oC.

A digital signal is one that varies in discrete steps. The signal does not vary smoothly but instead jumps from one level to the next with a sharp discontinuity.

Direct Drive:

Direct electrical contact from the microprocessor or controller to each pixel on a display. Used in simple glass displays with a few segments and icons, like a thermostat or digital meter. Also known as Static Drive. See also Multiplex.

Direct View

A term used to refer to active matrix liquid crystal displays (LCDs), cathode ray tubes (CRTs), plasma displays, and other displays that create the exact image that the user views. In contrast, projection displays need magnification optics to create the final image that is viewed.

DLP™

Digital Light Processor (DLP™), a proprietary technology developed by Texas Instruments as a micro display projection element. DLP uses an array of tiny mirrors on a silicon chip to reflect light from a projection lamp to form an image. Requires a lamp, color wheel, and optics to make front-projection and rear-projection displays.

A backlight in which the tube(s) are located at the side of the display and uses a scattering sheet to get even lighting across the display, which allows for thinner displays.

Elastomer:

Conductive rubber strip, also called Zebra Strip, used to connect the contacts on the glass display to the printed circuit board of a LCD character module. Also use in low resolution graphic modules. Electrical contact is made by compression with the bezel frame.

EL backlight:

A type of backlight using electroluminescent material. The thinnest available backlight. Electroluminescent can also be a type of display. Provides uniform light distribution over the active area. Requires an inverter to provide 90VAC at 400Hz. Low power consumption.

Electrochromic Display

This is a reflective display that uses electrochromic materials to switch pixels on and off. Electrochromic materials change color when the oxidation state of the material is changed by an applied voltage. NTERA is working on a display based on this technology. Electrically switchable automobile rear-view mirrors are an example of this technology.

Electrophoretic Display

This is a reflective display that uses electrophoresis to switch pixels on and off. Electrophoresis is the motion of charged particles suspended in a liquid in response to an electric field. Positively charged particles move toward the cathode, and negatively charged particles move toward the anode. If these particles are colored, the display shows different colors to the user as the particles move. E Ink and Gyricon are examples of this type of display.

EL

Electroluminescent (EL). This is a display technology based on the light-emitting ability of certain phosphors (typically ZnS) in an electric field. EL displays can be further subdivided into thick film, thin film, alternating current, and direct current type displays.

Emissive

A direct-view display, such as cathode ray tube (CRT), field emission display (FED), plasma, electroluminescent (EL), and organic light emitting diode (OLED), where the light generation, switching, and coloring are all done at once by the display. These displays do not need a separate backlight to provide light for the image. See also Transmissive, Reflective, and Projection.

The production lines that Corning’s customers use to create their products. The customers take our glass substrates and apply their own processes to create a final product. These are also referred to as fabs.

FED

A Field Emission Display (FED) is an emissive flat panel display that uses many small electron emitters to excite a phosphor screen and emit light. Also known as Thin CRT or carbon nanotube FED. This technology is still in the development phase and is not currently available commercially.

Finishing

This is the cold processing of the glass article to form the final product. Processes include cutting, grinding, polishing, and washing.

Forming

This is the processing of molten liquid glass into the basic shape of the end product. Typical forming processes include blowing and pressing, but for sheet glass the typical forming processes include, float forming and various downdraw processes, such as Corning’s proprietary Fusion process.

FPD

Flat panel display (FPD). FPD can be used to refer to any of a number of "flat" display technologies including LCD, plasma, FED, or others.

FRM:

Frame rate modulation.

FSTN:

Film Super Twist Nematic display. STN display with a film layer to improve contrast and viewing angle. This film also changes the display “on” color from blue to black.

Fusion

This is the proprietary process through which Corning produces LCD glass substrates. The fusion process begins when raw materials are blended into a glass composition, which is melted and conditioned to be homogeneous and virtually defect free. The molten glass is fed into a trough called an “isopipe,” filling it until the glass flows evenly over both sides. It then rejoins, or fuses, at the bottom, where it is drawn down to form a continuous sheet of flat glass.

Industry standard to define the mother glass size used in a LCD factory. Similar to wafer size used in a semiconductor fab (e.g., 6”, 8”, 12” wafers). LCD factories are designed with equipment for a specific mother glass size:

G2.5 = 370 x 470 mm G3.5 = 600 x 720 mm G5 = 1100 x 1300 mm

G5.5 = 1300 x 1500 mm G6 = 1500 x 1850 mm G7 = 1870 x 2200 mm

G7.5 = 1950 x 2250 mm G8 = 2160 x 2460 mm G9 = 2400 x 2800 mm

G10 = 2880 x 3080 mm

Graphic Display:

A display made up of an array of pixel elements in a matrix. Also called “dot matrix”. Can be used to display graphics, pictures and text.

High Definition Television (HDTV), a term that can refer to certain TV sets or programming that conforms to a set of standards that define next-generation television resolution, sound, and format. The most common HDTV formats in the U.S. are 480p, 720p, and 1080i, which correspond to lines of resolution and progressive or interlaced scanning. Each country or region has different HDTV definitions and standards.

Heat Seal:

A flat, flexible, adhesive connector which is bonded to the contact edge of the glass by heat. Used for high density connections in graphic modules.

HTPS

High-Temperature Poly-crystalline Silicon (HTPS), fabrication of poly-crystalline silicon through high temperature (>900C) processing steps. This process is used to make small thin film transistor- active matrix liquid crystal displays (TFT-LCDs) for projection displays, and requires the use of a synthetic quartz substrate.

Substrates that are Generation 5 and larger are classified as large-generation. Large-generation size substrates provide substantial cost efficiencies and greater output per substrate. Large-generation substrates not only allow customers to get more panels per sheet, but also to produce larger panels.

LCD (See also AMLCD)

Active matrix liquid crystal display (LCD). A display technology that uses a switch at each pixel to create high resolution and fast response times. One type of LCD in which the switch used is a thin film transistor (TFT), is known as a TFT-LCD. Displays based on this technology range from as small as 1" diagonal up to 40" diagonal.

LCD Module

A thin film transistor-passive or active matrix liquid crystal display (TFT-LCD) that contains all components, including backlight and driver integrated circuits (ICs), and is ready to be integrated into an end product such as a TV, monitor, notebook PC, or other device. This term is often used interchangeably with LCD panel.

LCD Panel

A thin film transistor-passive or active matrix liquid crystal display (TFT-LCD) that includes the array, color filter, and liquid crystal. May also include a backlight and driver integrated circuits (ICs), but sometimes is used to refer to just the glass-liquid crystal composite. Often used interchangeably with LCD module.

LCD Projection

A projection technology that uses small thin film transistor-active matrix liquid crystal displays (TFT-LCDs), of 2” diagonal or less, as picture elements. The light from the projection lamp is switched and given color by one of three TFT-LCDs, and then is combined into a picture by optics, and finally projected onto a screen. These can be used to make a rear-projection TV or a front-projection data projector.

LCoS

Liquid Crystal on Silicon (LCoS), a type of reflective micro-display that can be used to make front-projection, rear-projection, or near-eye displays. A thin film transistor (TFT) array is made on a silicon chip and becomes a display by adding a liquid crystal layer to control the reflection of light off the chip. A color wheel or color scroll, a light source, and a lens array are other system components needed for LCoS projection.

LED Backlights

LEDs are becoming the most popular type of backlight because they do not require an inverter, and they have a longer lifetime than EL or CCFL. Character modules and small graphic modules use yellow-green LEDs because they are lowest in cost and have the longest life. Monochrome FSTN and color modules require white LEDs, which are becoming lower in cost and longer in lifetime.

Lifetime

A measure of the durability of a display, expressed in how many hours of operation it takes for a display to show half the brightness as compared to the brightness it showed when it was new. For example, if a display is rated for 50,000 hours lifetime, it should take 50,000 of cumulative operation before it is half as bright as compared to when it was new. Most displays degrade slowly over time so the effect is not noticeable unless compared directly with a new display.

Liquid Crystal:

A liquid in which the molecules are arranged in a regular pattern. Usually used in LCD displays.

LTPS

Low temperature poly-crystalline silicon (LTPS). Lasers, or other low temperature energy sources, are used to crystallize amorphous silicon into a more conductive state known as poly-crystalline silicon (p-Si). This poly-crystalline silicon layer is patterned through photolithography to make a thin-film transistor (TFT) backplane. Active matrix liquid crystal displays (LCDs) made with LTPS backplanes are capable of higher resolution and better aperture ratio than LCDs made on amorphous silicon backplanes. Driver integrated circuits (ICs) can also be integrated into the backplane, for better form factor and higher quality. This is especially useful for small displays for mobile devices where smaller panels enable smaller and lightweight end products.

The process of converting the raw materials, that are used in glass-making, into a uniform, homogenous liquid. This involves both melting and dissolution reactions of the raw materials.

MEMS

Microelectromechanical systems (MEMS) are a class of micron-scale devices made using semiconductor processes that integrate electronic and mechanical functions. Texas Instrument's DLP™ projection element is one example of MEMS. Iridigm has also made a direct-view reflective display with MEMS technology. MEMS are also used for sensors, such as accelerometers and optical switches.

Micro corrugation

This refers to the fine-scale wrinkling of a glass sheet as a result of forming. This is typically seen with the forming of a thin glass sheet in a float process; it arises from a non-uniform glass response to the applied tensile or stretching force.

MTBF:

Mean Time Between Failures. This is the lifetime of the component or the system. System lifetime can be calculated from the lifetime of the individual components and the number of interconnects. Lifetime is usually expressed in hours. For LCDs, the lifetime is determined by the backlight. EL panels are the lowest, yellow-green LEDs are the highest.

Multiplex:

Method of sharing rows or columns of pixels on a display to reduce the number of connections to the driver or controller. As the display resolution increases, the multiplex rate must increase to allow all of the individual pixels to be addressed. See Direct Drive.

Organic light emitting diode (OLED), an emissive flat panel display that uses organic compounds to emit light. OLEDs can be passive or active matrix. Passive matrix devices are easier to make, but not capable of full color or high resolution. Currently, active matrix devices use a poly-crystalline silicon thin film transistor (TFT) array, similar to low temperature poly-crystalline silicon (LTPS) active matrix liquid crystal displays (LCDs). There has been limited production to date because of short product lifetimes and differential aging rates of the OLED materials. This is also known as Organic EL.

Organic EL

Organic electroluminescent (EL). This is an organic analog to the EL type display in which the active material is organic. This is another name for organic light emitting diode (OLED) technology.

Phase Alternation Line. International television standard which uses 625 lines per frame at 50Hz field rate.

Passive:

A technique by which each row and column of the display are multiplexed or addressed in turn (also can be referred to as Duty Type).

Passive matrix LCDs

These are the predecessors to active matrix liquid crystal displays (LCDs); these displays do not incorporate a thin film transistor (TFT) or switch at each pixel. As a result, they tend to have lower resolution, slower refresh rates, and poorer viewing angles than active matrix LCDs.

Photolithography

The patterning step of the process by which transistors are made for displays or microprocessors. Thin films of silicon or other materials are deposited on a substrate then covered with another material (photo resist) that reacts to light. This material is exposed to light through a mask that is patterned for one layer of the transistor. Then the exposed area is etched away, taking the underlying thin film with it. Then the photo resist is cleaned off, leaving the patterned thin film. This is repeated several times with different thin films to create the transistor array.

Pixel

An individual dot on the display. Short for "picture element," a pixel is the basic unit of information on a display. It can be made up of different colored sub-pixels.

Plasma

Emissive flat panel display technology that uses gas plasma to excite phosphors and make them glow. Used for large-size displays (typically 32" diagonal and up), but has a limited market because of the high cost of production. Also called plasma display panel (PDP).

Plasma Display:

A type of display produced by an electrical discharge that produces a red or white glowing image. Color filters are added to the white image o produce full color.

Polarizer:

This is a material that selectively transmits light with a given polarization. Polarizers are critical in the operation of most active matrix liquid crystal displays (LCDs), as the liquid crystal manipulates polarized light. A twisted-nematic (TN) LCD typically has polarizers on both sides of the LCD cell.

Poly-crystalline silicon TFT-LCD

Type of thin film transistor- active matrix liquid crystal display (TFT-LCD) that uses transistors made from poly-crystalline silicon rather than amorphous silicon.

Projection

A display that uses from one to three small emissive, reflective, or transmissive displays to create a picture that is enlarged by a set of optics to the final viewable size. The light is provided by a projection lamp, the switching is done by the small displays, and the color can be provided by the small displays or separate color elements. See also Emissive, Transmissive, and Reflective.

A display without a backlight. Reflective displays rely on ambient light to provide the image. Excellent for outdoors or bright light conditions. Most digital watches and calculators use reflective LCDs, although some color versions have been developed for mobile phones and PDAs. See also Emissive, Transmissive, and Projection. Emerging reflective technologies include Electrophoretic (made by E Ink and others), electrochromic (made by NTERA and others), and microelectromechanical systems (MEMS)-based (made by Iridigm and others).

Refresh Rate

The time interval required for the electronics to fully address a display. This rate determines the capability of the display to show video images.

Resolution

The number of pixels available for information display. More pixels (higher resolution) enables finer details to be displayed and generally results in a better image quality.

Response time:

Total delay time to change the image = decay time (Td, Toff) + rise time (Tr, Ton).

A single active area in the segmented displays (as opposed to the background area).

SHA:

Super High Aperture.

Silica

Silicon dioxide, this oxide forms the basis for most glass compositions.

STN

Super Twisted Nematic. A type of high-performance passive matrix display used to improve optical properties at high multiplex rates. Method is to increase the twist angle in the LCD construction from the 90 degrees used in TN to a much higher twist (270 degrees or more). Hence the nickname “super twist”. Used exclusively in character modules and graphic modules, including Color STN.

Sub-Pixel

A sub portion of a pixel showing only one of the primary colors - green, red or blue. Three or more sub-pixels make up a single pixel.

SVGA Resolution:

800x600 pixel count.

System-on-glass (SOG)

A thin film transistor-active matrix liquid crystal display (TFT-LCD) that has additional functionality, such as memory or computation, built into its array electronics. This can refer to almost any level of integration, from driver integrated circuits (ICs), to a full central processing unit (CPU). Requires low temperature poly-crystalline silicon (LTPS) backplanes, and is typically most valuable for small portable devices.

The LCD driver / controller is encapsulated in a bubble on a flex circuit. The flex is attached directly to the glass or a PCB.

TFT

Thin-film transistor (TFT). Electronic technology upon which active matrix liquid crystal displays (LCDs) are based. Each pixel is driven by a separate IC gate to speed the response time and improve the optics. The foundation of the TFT is a semiconductor layer (typically based on silicon) which can switch current flow on or off by the application of an electric field. The IC gates are deposited directly onto the LCD glass substrate in a combination of wafer fabrication and glass assembly.

TFT Array

A component of the LCD display. The glass substrate containing the thin film transistors used to switch the sub-pixels on or off.

TN:

Twisted Nematic. The original construction method for LCDs using 90 degree twist angles. Used in 7 segment and direct drive display applications. Very low cost manufacturing.

Touch Panel Controller:

The hardware element that translates the information between the touch panel and the host system.

Touchscreen:

A transparent glass or hard plastic sheet that mounts over the display viewing area and allows users to make a choice and input via touching the screen.

TQFP = Thin Quad Flat Pack

The LCD driver(s) / controller and other surface mount components are re-flowed onto a PCB.

Transflective:

A display that combines reflective and transmissive qualities. In dark ambient light environments, the backlight can be used to provide light for the display. In bright ambient light environments, the backlight can be switched off and the display used in reflective mode to save battery life. Most often used in PDAs and mobile phones. Good in sunlight and outdoor applications. Contrast ratio and brightness are decreased compared to transmissive type.

Transmissive:

A display that uses a backlight shining through the LCD to produce the image. Good in regular or dim lighting. Not for use in sunshine. Ambient light interferes with the backlight, and “washes out” the display image. The light is created by a CCFL or light emitting diode (LED) backlight, the switching is provided by the thin film transistor (TFT) array, and the color is provided by the color filter.

TSTN:

Triple Super Twist Nematic. Sharp name for film compensated super twist display which uses a retardation film to correct the color shift in STN displays, and so produces a black and white image.

The angle at which the viewer must be in comparison to the screen, in order to see the image on a display. For example, a 0° horizontal viewing angle is directly in front of the display and a 90° horizontal viewing angle is directly to the side. Emissive displays show the same brightness and color regardless of viewing angle, however, rear projection displays and transmissive displays can show some differences in color, brightness, and gray scale, with the most difference being noticed at the steepest viewing angles.

Conductive rubber strip, also called Elastomer, used to connect the contacts on the glass display to the printed circuit board of a LCD character module. Also use in low resolution graphic modules. Electrical contact is made by compression with the bezel frame.

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